Black men who have sex with men (MSM), especially young MSM, are more likely to contract HIV than White MSM. Research thus far has been unable to account for the mechanisms driving this racial disparity, as HIV research has largely targeted individual risk factors, but Black MSM consistently report comparable or fewer of these behaviors than other MSM. In addition, little research examining racial disparities acknowledges that substance use and other HIV risk behaviors are socially and spatially dependent; thus, differences in network and venue affiliation may shape the risk environments and behaviors of YMSM of different racial groups, and may be key in understanding differences in HIV. Emerging research with Black MSM documents racial differences in the network, venue, and neighborhood affiliations of YMSM. These findings suggest that although rates of drug use and other HIV risk behaviors may be lower among Black YMSM than other racial groups, their consequences may be different due to the nature of the risk environments experienced by these young men. The overall objective of this project is to contribute to knowledge about structural mechanisms (e.g., stigma and discrimination) that shape these risk environments, which in turn shape consequences of substance use and other HIV risk behaviors for young Black MSM. However, appropriately interpreting the empirical data describing these social and cultural contexts (i.e., the structure of social, sex, drug, venue, and neighborhood affiliation networks) i problematic without the incorporation of the voices, lived experiences, and knowledge of participants. Therefore, the innovative mixed methods approach proposed by this project will guide the interpretation of network-level structures captured within an existing NIH-funded cohort of YMSM. Three phases will occur in which network and geographic data is visualized (Phase 1) and used to guide interviews with YMSM, leading to a theory of mechanisms and functions in this population (Phase 2), which will be subsequently tested using multilevel modeling (Phase 3). The overall project has two aims: 1) identify how networks, venues, and neighborhoods operate as risk environments that shape the consequences of substance use and HIV risk behavior for YMSM of different racial groups, and 2) identify how structural mechanisms, such as stigma and discrimination, influence the networks, venue attendance, and neighborhood affiliations of YMSM of different racial groups.